Make http.url field opt-in (#70)

reqwest-tracing/CHANGELOG.md

@@ -5,7 +5,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
-- HTTP URL is captured in traces as the `http.url` attribute.
+### Added
+- `SpanBackendWithUrl` for capturing `http.url` in traces
 - Require an explicit otel name in the macros. Reduces cardinality and complies
   with otel specification for HTTP bindings.
 - Permit customisation of the otel name from the non-macro layer.

reqwest-tracing/src/lib.rs

@@ -96,9 +96,9 @@ mod reqwest_otel_span_builder;
 pub use middleware::TracingMiddleware;
 pub use reqwest_otel_span_builder::{
     default_on_request_end, default_on_request_failure, default_on_request_success,
-    DefaultSpanBackend, OtelName, ReqwestOtelSpanBackend, ERROR_CAUSE_CHAIN, ERROR_MESSAGE,
+    DefaultSpanBackend, OtelName, ReqwestOtelSpanBackend, SpanBackendWithUrl, ERROR_CAUSE_CHAIN,
-    HTTP_HOST, HTTP_METHOD, HTTP_SCHEME, HTTP_STATUS_CODE, HTTP_URL, HTTP_USER_AGENT,
+    ERROR_MESSAGE, HTTP_HOST, HTTP_METHOD, HTTP_SCHEME, HTTP_STATUS_CODE, HTTP_URL,
-    NET_HOST_PORT, OTEL_KIND, OTEL_NAME, OTEL_STATUS_CODE,
+    HTTP_USER_AGENT, NET_HOST_PORT, OTEL_KIND, OTEL_NAME, OTEL_STATUS_CODE,
 };
 
 #[doc(hidden)]

reqwest-tracing/src/reqwest_otel_span_builder.rs

@@ -1,7 +1,7 @@
 use std::borrow::Cow;
 
 use reqwest::header::{HeaderMap, HeaderValue};
-use reqwest::{Request, Response, StatusCode as RequestStatusCode};
+use reqwest::{Request, Response, StatusCode as RequestStatusCode, Url};
 use reqwest_middleware::{Error, Result};
 use task_local_extensions::Extensions;
 use tracing::Span;
@@ -88,7 +88,8 @@ pub fn default_on_request_failure(span: &Span, e: &Error) {
     }
 }
 
-/// The default [`ReqwestOtelSpanBackend`] for [`TracingMiddleware`].
+/// The default [`ReqwestOtelSpanBackend`] for [`TracingMiddleware`]. Note that it doesn't include
+/// the `http.url` field in spans, you can use [`SpanBackendWithUrl`] to add it.
 ///
 /// [`TracingMiddleware`]: crate::middleware::TracingMiddleware
 pub struct DefaultSpanBackend;
@@ -112,6 +113,26 @@ fn get_header_value(key: &str, headers: &HeaderMap) -> String {
     format!("{:?}", headers.get(key).unwrap_or(header_default)).replace('"', "")
 }
 
+/// Similar to [`DefaultSpanBackend`] but also adds the `http.url` attribute to request spans.
+///
+/// [`TracingMiddleware`]: crate::middleware::TracingMiddleware
+pub struct SpanBackendWithUrl;
+
+impl ReqwestOtelSpanBackend for SpanBackendWithUrl {
+    fn on_request_start(req: &Request, ext: &mut Extensions) -> Span {
+        let name = ext
+            .get::<OtelName>()
+            .map(|on| on.0.as_ref())
+            .unwrap_or("reqwest-http-client");
+
+        reqwest_otel_span!(name = name, req, http.url = %remove_credentials(req.url()))
+    }
+
+    fn on_request_end(span: &Span, outcome: &Result<Response>, _: &mut Extensions) {
+        default_on_request_end(span, outcome)
+    }
+}
+
 /// HTTP Mapping <https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/semantic_conventions/http.md#status>
 ///
 /// Maps the the http status to an Opentelemetry span status following the the specified convention above.
@@ -163,6 +184,21 @@ fn get_span_status(request_status: RequestStatusCode) -> Option<&'static str> {
 #[derive(Clone)]
 pub struct OtelName(pub Cow<'static, str>);
 
+/// Removes the username and/or password parts of the url, if present.
+fn remove_credentials(url: &Url) -> Cow<'_, str> {
+    if !url.username().is_empty() || url.password().is_some() {
+        let mut url = url.clone();
+        // Errors settings username/password are set when the URL can't have credentials, so
+        // they're just ignored.
+        url.set_username("")
+            .and_then(|_| url.set_password(None))
+            .ok();
+        url.to_string().into()
+    } else {
+        url.as_ref().into()
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -176,4 +212,32 @@ mod tests {
         let value = get_header_value("test", &header_map);
         assert_eq!(value, expect);
     }
+
+    #[test]
+    fn remove_credentials_from_url_without_credentials_is_noop() {
+        let url = "http://nocreds.com/".parse().unwrap();
+        let clean = remove_credentials(&url);
+        assert_eq!(clean, "http://nocreds.com/");
+    }
+
+    #[test]
+    fn remove_credentials_removes_username_only() {
+        let url = "http://user@withuser.com/".parse().unwrap();
+        let clean = remove_credentials(&url);
+        assert_eq!(clean, "http://withuser.com/");
+    }
+
+    #[test]
+    fn remove_credentials_removes_password_only() {
+        let url = "http://:123@withpwd.com/".parse().unwrap();
+        let clean = remove_credentials(&url);
+        assert_eq!(clean, "http://withpwd.com/");
+    }
+
+    #[test]
+    fn remove_credentials_removes_username_and_password() {
+        let url = "http://user:123@both.com/".parse().unwrap();
+        let clean = remove_credentials(&url);
+        assert_eq!(clean, "http://both.com/");
+    }
 }

reqwest-tracing/src/reqwest_otel_span_macro.rs

@@ -52,7 +52,10 @@
 /// ```
 ///
 /// If nothing else is specified, the span generated by `reqwest_otel_span!` is identical to the one you'd
-/// get by using [`DefaultSpanBackend`].
+/// get by using [`DefaultSpanBackend`]. Note that to avoid leaking sensitive information, the
+/// macro doesn't include `http.url`, even though it's required by opentelemetry. You can add the
+/// URL attribute explicitly by usng [`SpanBackendWithUrl`] instead of `DefaultSpanBackend` or
+/// adding the field on your own implementation.
 ///
 /// You can define new fields following the same syntax of [`tracing::info_span!`] for fields:
 ///
@@ -95,6 +98,7 @@
 ///
 ///
 /// [`DefaultSpanBackend`]: crate::reqwest_otel_span_builder::DefaultSpanBackend
+/// [`SpanBackendWithUrl`]: crate::reqwest_otel_span_builder::DefaultSpanBackend
 /// [`default_on_request_success`]: crate::reqwest_otel_span_builder::default_on_request_success
 /// [`default_on_request_failure`]: crate::reqwest_otel_span_builder::default_on_request_failure
 /// [`default_on_request_end`]: crate::reqwest_otel_span_builder::default_on_request_end
@@ -129,7 +133,6 @@ macro_rules! reqwest_otel_span {
                         http.method = %method,
                         http.scheme = %scheme,
                         http.host = %host,
-                        http.url = %url,
                         net.host.port = %host_port,
                         otel.kind = "client",
                         otel.name = %otel_name,